System of multifrequency circuits



March 1 1927.

R.- W. DEARDORFF SYSTEM OF MULTIFREQUENCY CIRCUITS Filed Feb. 8. 1924ATTURNEY Patented Mar. 1, 1927.

1,619,060 s PATENT oFFICE.

RALPH W. DEARDORFF, OF KENSINGTO N, CALIFORNIA, ASSIGNOR TO AMERICANTEL- EPHONE AND TELEGRAPH COMPANY, A CORIQRATION OF NEW YORK.

SYSTEM F MUL rirnnennncr ciRcUrrs;

Application flied February s, 1924. serial No. 691,455.

The principal object of to provide apparatus particular frequency rangeto another.

quency currentspart way and transmitting them the rest of the way a partof another low These and other other phantom circuit. p

will become appar jects of my inventionl on consideration of a Vlimitednumber of sy cific embodiments which I have chosen illustratein theaccompanying drawings.

will be understood that the following speciparticularly to ytheseexamples of my invention, leaving the scope defined in theappendfication`v refers more ofthe invention to be ed claims.

`In the drawings, Figure means for transferring rents from a part of onesuch circuit a party vof the other `such* circuit. fFig. pairs of sideto a phantom circuit, with meansv to transfer high fre-` 2 is a diagramshowing two circuits,l each pair belonging quency currents from a part*ofy each s circuit" of taining the normal transmission' side andphantom circuits o-f both pairs.

' In the transmission filter 13 is interposed'asY shown in Fig.

filter consists of reactance elementsV arranged asshown, and in thepar-KV ticular' instance here disclosed, the reactanceV the followingtable.Y

Ythe table 'also 4U This low pass in the foregoing Y m11. L1=532L27-65.8 1132329 11,216.4

llith the values given the critical frequency 13 is 8,(190 cy les per4second.

my invention is new and improved method and for the transfer of currentsof a fromv one circuit Another object of my invention isfto provide fortransmitting high freon a part of a low frequency circuit and thentransferring them frequency circuit. Still another object of myinvention is to provide for transferring currents of a certain frequencyrange from the side circuits of a phantom circuit to the side circuitsof an- Y 1 isa diagram'of twov low frequency circuits provided 'withhighV frequency curone pair tov'a part of a respective side Vcircuit Vofthe other pair, while mainover the line 11, 12, a'low pass comprises allthe reactance values'in; Figs. 1l

l table, l for the low pass filterV vThat is, frequencies below thisvalue will be transmitted between the lines 11, 12 and frequencies abovethis value will be shunted out.

At 14, 15 a similar transmission line is shown with a similarlyinterposed low pass filter 16.

The high pass wave filter 18 is connected at 17 and v21 between theparts 11 and 15 of the respective lines 11,12 and 14, 15. This highpasslter 18 is made up of reactances arranged as shown inthe drawing andwith the particular values given in the foregoing table.V Its critcialfrequency is 3,000 cycles Vper second, meaning that frequencies abovethis value will be transmitted between 11, 17V and 15, 21 but thatfrequencies below this value will not be transmitted.

Voice frequency currentsY on the line 11, 12 will pass readily .throughthe filter 13 and will not be diverted at 17. Similarly, voice frequencycurrents will'pass on the line 14, 15 without diversion at 21. But highfrequency currents on the part 11 of the line 11,12 will not pass to thepart 12 but will pass at 17 through the filter 18 to the part from 15 to11. v

VIt will be seen that at. any place where -two voice frequencytransmission lines pass in proximity, filters like 18 and 16 canlt-.erposed and another filter like 18 can beconnected across so thathigh frequency lcurrents may be transferred from one part 11 of one lineto one part 15 of the other line.

In Fig. 2 I have shown two side circuits 11, 12 and 11, 12 phantomcircuit. Similarly, 14, A15 and 14', 15 Vare the two side circuits ofanother phantom circuit. In each sidecircuit there is interposed arespective low pass filter 13, 13, 16 and 16. v l18 'are connectedacross between parts of respective side circuits in a manner similar tothat described for Fig. 1. At the middle points 19 and 19 of theterminal shuntcoils '11 connections are made across from one high passfilter 18 to the other high pass filter Y 18. These connectons 19 and 19are made through interposedv condensers C5. The l middle coils L, havetheir middle points dirrectly connected at 20. v It will be seen thatthe four side circuits shown in Fig. 2 will each carry voice frequencycurrents, the respective low pass filters LP transmitting these currentsfreely.

ide

bein.- 8

which together make a` High pass filters 18 and:v

Also, for voice frequency currents on any side circuit, the high passfilters 18 and 18 will not transmit, the principle being the same as inFig. 1. This is not altered by the connections at the middle points ofthe coils L4 in Fig. 2, because these points are neutral points on theside circuits.

High frequency currents on the side circuits will be blocked by the lowpass filters LP and will be transmitted by the high pass lters 18 and18'. I-Iere again the connections at the middle points of the coils L4will not affect this result, because these points are neutral points onthe side circuits.

Low frequency currents on the phantom circuits will be readily passed bythe low pass filters as may be seen from Fig. 1, Where the inductancesL, are non-inductive for currents the same way in both conductors. Inthe absence of the connections 19-I 19 and 20, phantom currents, thoughof low frequency, would get through the condensers C3 and C4 in somedegree between the lines 11, 1l' and 15, 15. But the cross connections19-19 and 2O shunt out such phantom currents so that no substantialphantom current gets across between 11, 11' and 15, 15. The capacitiesC5 are given a compromise value; if too large, they would shunt out somuch current across 11, 11' or 15, 15 as seriously to attenuate thephantom current along the phantom circuit 11, 12, 12', 11' or 15, 14,14', 15'. On the other hand, if the capacities C5 were made too small,there would be an appreciable transfer of phantom current between 11,11' and 15, 15'. By putting condensers of proper value at C5, it ispossible to put a direct connection at 2O so that substantially nocurrents are transferred across from one vpliantom circuit to the other.

It should be noted that by making the connections at the middle pointsof the coils L4, these coils become non-inductive to phantom currents,so that they oeriio impedance whatever in Vthe cross connections 19-19and 20.

I have shown the reactances at C5 in Fig. 2 in the form of capacitiesbut it will be understood that any substantial reactancesy for the voicefrequency range'might be employed at these points. Instead of thecapacities represented by the condensers C5, inductances or resistancesmay be interposed as indicated in Fig. 2 by throwing the switches S tothe proper contacts. If the switches S are thrown so as to substitutethe inductances for the condensers C5, the combination of which theseinductances are apart would act as a high pass wave filter to thephantom circuit 11-11-- 15-15'.

It will be seen that if the phantom circuit` comprising the sidecircuits 11, 12 and l1',

12 passes in proximity to the phantom circuit comprising the sidecircuits 14, 15 and 14', 15', then it becomes possible to superpose highfrequency currents on parts 1l, 11 of the side circuits of one pair andthe parts 15, 15' of the side circuits of the other pair and to transferthese high frequency currents across either way.

I claim:

1. In combination, two phantom circuits each comprising a pair of sidecircuits, low pass filters interposed in said side circuits, andconnect-ions between the parts of the side circuits one way of one pairto the parts of the respective side circuits one way of the other pair,these connections each comprising a high pass wave filter and means toshunt out phantom currents across said high pass filters.

2. rllwo phantom circuits, each comprising a pair of side circuits, lowpass filters interposed in each said side circuit, high pass filtersconnecting each side circuit on one side in each phantom with acorresponding side circuit on one side in the other phantom, andconnections between the midpoints of corresponding shunt elements of thesaid last mentioned filters, the connections for the end shunt elementscomprising switches and various impedance elements which may beinterposed by means of said switches.

3. In combination, two phantom circuits passing in proximity and eachcomprising a pair of side circuits, low pass lters inter-f posed in therespective side circuits, connections across from one part of eachsidecircuit of a pair to a part of a respective side circuit of theother pair, high pass wave filters interposed in these connections, saidhigh pass wave filters comprising the. usual shunt and seriesreactances, and connections from the middle oints of the shuntvreactances of one hig pass Wave filter to the corresponding points ofthe other high pass wave filter.

4. In combination, two phantom circuits passing in `proximity and eachcomprising aV pair of side circuits, low pass lters interposed in therespective side circuits, connections across from one part of each sidecircuit of a pair to a part of a respective side circuit of the otherpair, high pass wave filters interposed in these'connections, said highpass wave filters comprisingseriescon-l densers balanced in pairs andalternately disposed shunt inductances, the Vterminal shunt inductances,of each filter being connected at their middle points through condensersto the like and the intermediate inductances beingconnected at theirmiddle points directly to the like points of the other filter.;V Y 1 5.In combination, ytwo phantom circuits each comprising apair ofside'circuits 'all adapted for through transmission Ofcurpoints of theother filter,

rents of a certain frequency range, means to transfer currents ofanother frequency range between a side circuit of one pair and a sidecircuit of the other pair, and means to prevent current of said firstfrequency range from getting across from one phantom circuit to theother.

6. In combination, two phantom circuits each comprising a pair of sidecircuits and adapted for through transmission of currents of a certainfrequency range, means to transfer currents of another frequency rangebetween a part of each side circuit of one pair and a part of arespective side circuit of the other pair, and means to prevent currentof said first mentioned frequency range from getting across from onephantom circuit to the other.

7 In combination, two phantom circuits each comprising a pair of sidecircuits, low pass filters interposed in the respective side circuits,high pass filters interposed between a part of each side circuit of onepair and part of a respective side circuit of the other pair, and meansto prevent low frequency currents on either phantom circuit from gettingacross through the connections afforded by said high pass filters.

8. In combination, two phantom circuits passing in proximity and eachcomprising a pair of side circuits, low pass filters interposed in therespective side circuits, connections across from one part of each sidecircuit of a air to a part of a respective side circuit o the otherpair, high pass wave filters interposed in these connections, said highpass wave 4filters comprising series condensers balanced in pairs andalternately disposed shunt inductances, the terminal shunt inductancesof each filter' being connected at their middle points through impedanceelements to the like points of the other filter, and the intermediateinductances being connected at their middle points directly to Ythe likepoints of the other filter.

In testimony whereof, I have signed my name to this specification this29th day of January, 1924.

RALPH IV. DEARDORFF.

